This research is directed at discerning the biochemical mechanisms by which the synthesis and secretion of human placental lactogen (hPL) is modified during normal gestation and trophoblastic disease. To this end, we wish to study rates of hPL turnover in placental tissue, translation and transcription of hPL-specific mRNA, and the number of hPL specific gene copies in placental DNA and chromatin. Turnover and secretion rate studies utilize tissue fragments in a flow-through apparatus. The estimation of translation, transcription and gene copy measurements employ the synthesis of DNA which is complementary to hPL-specific mRNA. This cDNA is used as a probe in nucleic acid hybridization experiments to estimate the number of hPL mRNA and gene sequences present in normal and abnormal placental tissues.